There has been known a pin-contact type inspection system for inspecting the presence of defects in circuit patterns or conductive patterns formed on a board. The pin-contact type inspection system is constructed to inspect the electrical conduction between both ends of a conductive pattern as an inspection object, in accordance with a resistance value of the conductive pattern obtained by bringing a pair of pin probes into direct contact with the ends of the conductive pattern, respectively, and detecting a voltage which is generated at one of the pin probes in response to a certain current supplied to the other pin probe.
The pin-contact type inspection system is advantageous to have a high S/N ratio because the pin probes are brought into direct contact with the conductive pattern. On the other hand, in inspecting a board having conductive patterns arranged at a fine pitch, the pin-contact type inspection system will be suffered from difficulties in bringing the pin probes into contact with an intended conductive pattern, and in adequately positioning the pin probes even if they can be successfully brought into contact with the intended conductive pattern.
In view of this problem, a non-contact/contact combination type inspection system has been proposed in which an inspection signal including an AC component is applied to a pin probe in direct contact with one end of a conductive pattern as an inspection object, and the inspection signal is detected from a probe positioned such that it is spaced apart from the other end of the conductive pattern in a non-contact manner, through the capacitive coupling between the non-contact probe and the conductive pattern.
Since the non-contact/contact combination type inspection system allows the need for being in direct contact with the conductive pattern as in the pin probe to be eliminated from the non-contact probe at the other end of the conductive pattern, the positioning accuracy of the non-contact probe can be roughly set up. In addition, the non-contact probe can be designed such that it is commonly used for a plurality of conductive patterns to reduce the number of probes. Therefore, the non-contact/contact combination type inspection system can handle a board having conductive patterns arranged at a fine pitch.
There has also been known a slide type inspection apparatus comprising a pair of probes adapted to be slidably moved in a synchronous manner while being sequentially located at both ends of each of conductive patterns, respectively. This slide type inspection apparatus can advantageously eliminate the need for preparing a dedicated jig for each of different boards.
In the aforementioned pin-contact type and non-contact/contact combination type inspection systems, the arrangement of the probes at both ends of each of conductive patterns and/or the processing of detected signal from one of the probes is varied depending on the distance or pitch between the adjacent conductive patterns. Thus, these systems can inspect only one kind of board having a predetermined configuration of conductive patterns, and a jig to be used therein has to be prepared in conformity with each of different configurations of conductive patterns.
The slide type inspection apparatus is workable on the condition that the pitch between adjacent conductive patterns in one ends thereof is approximately equal to that in the other ends. If there is a difference between the respective pattern pitches in one ends and the other ends of the conductive patterns, any inspection becomes impossible because the probes cannot be located at both ends of each of the conductive patterns, respectively, in a synchronous manner or at the same time.
In view of the above problems, it is therefore an object of the present invention to provide a circuit-pattern inspection apparatus capable of readily inspecting the presence of defects in conductive patterns, for example, even if a probe is positioned to both ends of the conductive patterns in a non-contact manner, and there is a difference between the respective pattern pitches in one ends and the other ends of the conductive patterns.